1. Field of the Invention
This invention relates to a cable waterproof structure, a wire harness using the cable waterproof structure, and a method of manufacturing the wire harness.
2. Description of the Related Art
An electric brake system is used for vehicle such as an automobile. An Electro-Mechanical Brake (EMB) device and an Electric Parking Brake (EPB) device are known as the electric brake system.
The EMB device is simply referred to as “electronic brake” or “electric brake”. The EMB device is configured to generate brake force depending on driver intention by controlling rotation driving force of respective electric motors provided on each wheel of vehicle in accordance with a brake pedal manipulated valuable (leg-power or displace amount) of driver and by pressing a brake pad to a disc rotor of wheel by a piston driven by the electric motor.
The EPB device is configured to generate the brake force by driving the respective electric motors provided on each wheel of vehicle by operating a parking brake start switch after stopping vehicle by the driver and pressing the brake pad on the disc rotor of wheel by the piston driven by the electric motor.
A vehicle often comprises sensors on the wheel such as a wheel speed sensor (it is also referred to as an Anti-lock Brake System (ABS) sensor) detecting firming wheel speed, an air pressure sensor detecting air pressure in a wheel, and a temperature sensor.
A wheel side and a vehicle side are connected by using a compound cable housing signal lines such as a signal line for the sensor mounted on the wheel and a signal line for the EMB device to control, and a power line to supply power to the EMB device or the electric motor for the EPB device.
Since a wire harness using the compound cable has different destinations of a plurality of insulated wires (the signal line and the power line described above) included in the cable, it is necessary to separate the insulated wires in accordance with the destinations. Since water may enter into a sheath over the insulated wires at the separated part of the insulated wires, it is necessary to ensure waterproofness at the separated part.
For example, covering the entire separated part by resin mold is known as the waterproof structure ensuring the waterproofness at the separated part of the insulated wire. However, in such configuration, the waterproof structure cannot ensure the waterproofness since the resin mold fails to closely adhere to an insulator when the resin mold comprises urethane resin and the insulator of the insulated wire comprises polyurethane. Providing a heat shrinkable tube with adhesive additionally to cover the resin mold, and the insulated wire and the cable extended from the resin mold is also known. However, it takes many times in manufacturing since it is necessary to provide the heat shrinkable tube with adhesive with respect to extending destinations of the wires and the cables.
The inventors consider ensuring the waterproofness at the separated part by covering the sheath and the insulated wire extended from an end of sheath collectively with the heat shrinkable tube with adhesive.
When only the heat shrinkable tube with adhesive is provided, the adhesive melts and the resin tube shrinks again under high temperature environment, for example, at not less than 120° C. Thus, the inventors confirm that the resin tube may be slipped out of the sheath. Although the inventors consider fastening and fixing a part of the resin tube that covers the sheath tightly by using INSULOK (a registered trademark for a cable tie) the inventors confirm that the resin tube slips out under the high temperature environment even when using the INSULOK.
JP 2015/073414 A discloses the cable waterproof structure that covers the sheath and the insulated wire extended from the sheath collectively by using the heat shrinkable tube with adhesive, and provides a low temperature shrink type t shrinkable tube of which the shrinkage start temperature is lower than the shrinkage start temperature of the heat shrinkable tube with adhesive so as to cover the end of heat shrinkable tube with adhesive and the sheath collectively. The structure disclosed by JP 2015/073414 A can prevent the resin tube from slipping out under the high temperature environment.